// Utility function that allows modes to be combined. The mode given
// as the base argument takes care of most of the normal mode
// functionality, but a second (typically simple) mode is used, which
// can override the style of text. Both modes get to parse all of the
// text, but when both assign a non-null style to a piece of code, the
// overlay wins, unless the combine argument was true, in which case
// the styles are combined.

// overlayParser is the old, deprecated name
CodeMirror.overlayMode = CodeMirror.overlayParser = function (base, overlay, combine) {
    return {
        startState: function () {
            return {
                base: CodeMirror.startState(base),
                overlay: CodeMirror.startState(overlay),
                basePos: 0, baseCur: null,
                overlayPos: 0, overlayCur: null
            };
        },
        copyState: function (state) {
            return {
                base: CodeMirror.copyState(base, state.base),
                overlay: CodeMirror.copyState(overlay, state.overlay),
                basePos: state.basePos, baseCur: null,
                overlayPos: state.overlayPos, overlayCur: null
            };
        },

        token: function (stream, state) {
            if (stream.start == state.basePos) {
                state.baseCur = base.token(stream, state.base);
                state.basePos = stream.pos;
            }
            if (stream.start == state.overlayPos) {
                stream.pos = stream.start;
                state.overlayCur = overlay.token(stream, state.overlay);
                state.overlayPos = stream.pos;
            }
            stream.pos = Math.min(state.basePos, state.overlayPos);
            if (stream.eol()) state.basePos = state.overlayPos = 0;

            if (state.overlayCur == null) return state.baseCur;
            if (state.baseCur != null && combine) return state.baseCur + " " + state.overlayCur;
            else return state.overlayCur;
        },

        indent: base.indent && function (state, textAfter) {
            return base.indent(state.base, textAfter);
        },
        electricChars: base.electricChars,

        innerMode: function (state) {
            return {state: state.base, mode: base};
        },

        blankLine: function (state) {
            if (base.blankLine) base.blankLine(state.base);
            if (overlay.blankLine) overlay.blankLine(state.overlay);
        }
    };
};
